Mercury arc



PF.SCOHELD MERCURY ARG Oct. 16, 1934.

Filed Jan. 28, 1933 INVENTORT m E Y E s n ...J/A m L w ,P

Patented Oct. 16, 1934 UNITED STATES FFCE MERCURY ARC Application January 28, 1933, Serial No. 654,082

1 Claim. Y (Cl. Z50-27.5)

My invention relates to a mercury arc and more particularly to such a device which may be rotated in order to strike the arc.

Among the objects of my invention are: To

' provide a mercury arc in which the rotation of the envelope will strike the arc; to provide a simple means for striking the arc in a mercury arc rectier; to provide a mercury arc rectifier in which rotation of the envelope will simultaneously strike the arc and switch exterior circuits; and to provide a simple and inexpensive mercury arc rectifier.

Other objects of my invention will be apparent or will be specifically pointed out in the description formingfa part of this specification, but I do not limit myself to the embodiment of my invention herein described, as various forms may be adopted within the scope of the claim.

In the accompanying drawing which illustrate a preferred form of my invention:

Figure 1 is a plan view, partly in section of the mercury arc as mounted on a panel.

Y Figure 2 is an end view, the starting resistance being diagrammatically illustrated.

Figure 3 is a cross sectional view taken along a plane indicated by the line 3-3 in Figure 1, the arc being in the starting position.

l Figure 4 is a sectional view taken as in Figure l 3, showing the arc in running position.

Figure 5 is a diagram, reduced to lowest terms of a circuit adapted to utilize the arc as a rectier.

g t In broad terms my invention comprises an envelope having an annular expansion chamber therein containing a quantity of mercury. A cathode lead is sealed into the envelope and extends around the inner periphery cf the cham- I ber. An anode lead, or in case a full wave arc is desired, two anode leads are sealed through the envelope and terminate near the cathode lead, but do not touch the cathode. When the envelope is rotated so that the mercury occu- A zpies a position in the chamber at the point where -the anode lead approaches the cathode lead, the two leads both contact the mercury. When the envelope is rotated to a new position this double contact is broken and the mercury is in contact with the cathode lead alone. I prefer to operate a switch also by the envelope rotation so that when the cathode and anode leads are shorted by the mercury a resistance is in circuit with the anode supply, and when the arc is started by the rotation of the envelope, that same rotation actuates the switch to remove the resistance from the circuit. As is well known in the art, the spark which occurs when the circuit is broken by the mercury moving to its new position, will start the arc.

Referring directly to the drawing, an elon- G0 gated envelope 1 of heat-resisting glass, quartz or like materials, is provided with an annular expanded portion 2 which forms an arc chamber 3. `A cathode lead 4 pierces the envelope at a cathode seal 5, preferably through the outer rim 65, of the expanded portion. Upon entering the arc chamber, the lead is extended around the cire cumference of the chamber to form a cathode extension 6. l prefer to extend this lead for at least a quarter turn. Two anode leads 7 are 70. sealed through the opposite ends of the envelope, extend along the central axis of the device until they enter the arc chamber. The leads are then bent sharply, preferably vat right angles to form anode terminals 8, ending adjacent but not 75. touching the cathode extension. Both anode terminals should lie in the same radial line of the chamber. 1t is desirable, but not necessary, that the anode terminals end adjacent the cathode lead at the cathode seal.

A quantity of mercury 9 is introduced into the tube, of suiiicient amount that it will short the anode and cathode leads when the envelope is rotated so that the anode terminals are directed downwardly.

The device is then evacuated in the approved manner for mercury arcs, sealed from the pumps, and mounted.

As the device is to take advantage of gravity to hold the mercury in the arc chamber, I prefer to mount the envelope horizontally as shown in Figures 1 and 2.

Metal caps 10 are cemented to the opposite ends of the envelope, the anode leads are electrically connected to the caps, which are then 9 used as trunnions for the rotation of the envelope in bearings 11, formed in brackets 12 fastened to a panel, or other convenient support 13 by rivets 14. The brackets should preferably be of insulating material, as they carry switch contacts 15, the contacts being bent to form an arm socket 16.

Each anode cap is formed with an axial end shaft 1'7 to which is attached a switch arm 18, 105 bent to cooperate and enter the arm socket 16.

A handle 18 is cemented over the cathode seal 5 and a flexible cathode lead 19 is fastened to the cathode lead 4 through a hole 20 in the handle. This iiexible lead terminates in a cathode post 110 21 on the panel, and is long enough to allow p for rotation of the device by means of the handle.

A switch arm post 22, on the panel is connected by switch wire 23 to the switch arm 18, and an anode post 24 is connected to the anode cap by a flexible anode lead 25.

A suitable ballast resistor 26 indicated diagrammatically in Figure 2, is connected between the anode post and the switch arm post.

Referring directly to Figure 5, a transformer 27 is connected to feed the anode through anode wires 28. I have shown the resistors 26 as capable of being shorted out by the closing of the switch formed by the arm 18 and the switch contact 15.

The secondary of the transformer is provided with a center tap 29 and a cathode wire 30 goes directly to the cathode after passing through the load, as shown.

In the preliminary adjustment of the device, the envelope is mounted on its bearings, and rotated until the handle points directly down. In this position the mercury will cover the point where the cathode lead enters the chamber, and will also short the cathode to the anode leads by direct conduction through the mercury.

In this position of the envelope, the switch arms 18 are adjusted to point down also, 99 removed from the switch arm sockets 16. The arms are then solidly secured to the axial shafts.

The arc is then connected in the circuit as described, and the current may then be turned on from the mains into the transformer.

As the current starts, with the handle in the downward position, the resistors 26 are in series with each anode, preventing overload due to the direct short within the tube. With the current still on, the handle is rotated 90, to the front, the mercury moving to a new position as shown in Figure 4. As it moves to the new position the contact with the anode lead is broken, but the mercury still maintains contact with the cathode lead. The spark which takes place when the anode contact is broken vaporizes enough mercury vapor to start the arc, and it will then maintain itself until the current is broken.

It is of course obvious that only one resistor may be used if desired, and that if a single anode is used, particularly on low powers, the switch may be eliminated, the load itself acting as ballast. It is also obvious that other mounting structures may be used in which the envelope may be rotated. In all cases, however, the arc is started by the rotation of the envelope to cause the mercury to break a short between anode and cathode, but still remain in contact with a cathode lead.

I claim:

In combination, a mercury arc comprising an envelope adapted to be rotated around a horizontal axis, said envelope having van annular channel therein, a cathode lead sealed through said envelope and extending along the inner periphery of said channel, an anode lead sealed through said envelope and terminating adjacent said cathode lead, an energizing circuit for said anode, a quantity of mercury in said channel of a quantity sufficient to contact both of said leads in one position, means for rotating said envelope to start said arc by causing said mercury to move to a new position wherein said mercury is in contact with said cathode lead only, and means attached to said envelope operable by said rotation to insert a resistance in said anode energizing circuit when said mercury is contacting both said anode and cathode leads.

PHILIP F. SCOFIELD. 

